Hello,
I just want to point out that the voice from the text to speech option doesn't come from the game; it comes from your computer/device. So the devs can't really do anything about the voice itself. You should be able to change the voice and its speed in your device's accessibility features. (The "talking in code at the end" is, I think, the voice reading the name of the character who's speaking + the letters from the week in the upper corner – I don't know if reading the days' letters can be disabled or not by the devs, though.)
(Also, otome visual novels are very rarely multiplayers given how the narrative works… I can't speak for your other questions, though.)
Have a nice day.